An isolated DC-DC converter can be built from a transformer, a controller, and a handful of discrete parts—or bought as a module that packages all of it into one component. For gate-drive supplies, industrial control boards, and sensor power, the module is often the engineering-correct choice: it moves the isolation design, the magnetics, and the safety certification from the system designer to the module maker. This article explains the specifications that matter, how to size a module for gate-drive power, and where the module’s isolation rating and certification decide the selection.
Why an Isolated Module Instead of a Discrete Converter
The discrete approach gives control over every component and the lowest part cost at volume; the module gives a qualified, tested, certified power stage that removes the design risk. The decision factors:
| Consideration | Discrete isolated converter | Isolated DC-DC module |
|---|---|---|
| Design effort | Transformer, controller, feedback design | Select the module |
| Isolation certification | System-level design and test | Module carries the isolation rating |
| Magnetics | Designer-specified | Module maker-controlled |
| Layout | More parts, more board space | Compact, one component |
| Cost | Lower at high volume | Higher part cost, lower NRE |
The module wins where the isolation design is not the product’s core competency, where certification time matters, or where board space is tight—the typical gate-drive and industrial-control context.
The Specifications That Matter
Input and output voltage. The input range must cover the system rail (for example 12 V, 24 V, or 48 V) with margin; the output must match the load, commonly a gate-drive rail (e.g., 15 V, 20 V, or a bipolar +15/−5 V for SiC drivers) or a logic rail.
Output power. The module’s rated power must cover the load’s peak, not just the average. A gate driver draws pulsed current during switching; the module’s transient response and its peak-current capability matter as much as the continuous rating.
Isolation voltage and rating. The isolation rating (for example 1–3 kV DC or 5 kV RMS for reinforced applications) must clear the system’s voltage and the safety standard. The isolation class—functional, basic, or reinforced—comes from the end-equipment standard, and the module’s certificate is the evidence.
Regulation and ripple. The output regulation and ripple define the noise on the load. Gate-drive rails are noise-sensitive: the module’s ripple and its transient response to pulsed loads affect the drive waveform quality.
Temperature range and derating. The module’s operating temperature and its derating curve set the usable power in the enclosure; a module rated at 2 W at 25 °C may derate to 1.2 W at 85 °C.
Isolation Ratings and Certification Fields
Isolation is the module’s core spec, and three terms are often confused:
- Working voltage is the continuous voltage the isolation must withstand over the product’s life—the number the design starts from;
- Isolation test voltage is the higher, short-duration withstand voltage used for type testing and production checks;
- Reinforced (or basic/functional) isolation is the safety class defined by the end-equipment standard, which sets the required margins and the creepage/clearance.
The selection fields that matter on the datasheet and the certificate:
| Field | What it answers |
|---|---|
| Certification body and certificate number | Whether the isolation claim is independently verified |
| Working voltage and test voltage | The continuous and withstand capability |
| Pollution degree and altitude derating | How the environment reduces the ratings |
| Creepage and clearance | The physical distances for the working voltage |
| EMC filter requirement | What the module needs from the board to meet emissions targets |
| MTBF definition | The reliability basis and its conditions |
The fields belong in the comparison sheet: two modules can both say “isolated” and differ by an order of magnitude in the working voltage or the certification route.
Sizing for Gate-Drive Power
The gate-drive supply is the classic module application, and the sizing is arithmetic:
- Estimate the gate-drive energy. Each switching event needs Qg × VGS of energy; at frequency fsw, the average power is Qg × VGS × fsw per driver channel. A 100 nC gate at 20 V switched at 100 kHz needs 0.2 W per channel.
- Add the driver quiescent power. The driver IC’s supply current at the operating frequency adds a constant term.
- Sum the channels and the margin. A six-channel system with the numbers above needs roughly 1.5–2 W plus margin; a 3 W module covers it with headroom.
- Check the peak. The turn-on transient draws more than the average; the module’s transient response and output capacitance must hold the rail within the driver’s UVLO window during the switching edge.
The figures are method illustrations; the real inputs come from the driver datasheet and the switching frequency. The gate-drive sizing and timing logic is covered in the companion gate-drive articles in this series; the module supplies the isolated rail those designs need.
A Worked Sizing Example
Size an isolated module for a three-phase SiC inverter’s gate-drive supply: three high-side drivers plus three low-side drivers, each switching a 150 nC gate at 18 V and 50 kHz.
- Gate-drive energy per channel: 150 nC × 18 V = 2.7 µJ per edge, doubled for the charge and discharge cycle, at 50 kHz gives about 0.27 W per channel.
- Six channels: about 1.6 W total gate-drive power.
- Driver quiescent and losses: add roughly 0.5–1 W for the driver ICs and the module’s own losses.
- Peak versus average: the turn-on edges draw current in short bursts; the module’s transient response and output capacitance must hold the rail above the driver’s UVLO during the edge.
- Selection: a 3 W module covers the ~2.5 W budget with margin; a 2 W module fails the peak check unless the capacitance and the driver’s UVLO margins tolerate it.
The values are example inputs for method. The lesson is that the module is sized from the peak and the transient, not from the average power—a gate-drive supply that looks like 2 W on paper can need a 3 W module in practice.
Derating check. The same module at 85 °C ambient may derate to 60–70% of its 25 °C rating; the usable power at the operating temperature, not the catalog rating, is the selection number. The derating curve is a required page in the comparison.
Ripple, Transient Response, and Cross-Regulation
The module’s quality shows in the noise and the transient behavior, which matter more for gate-drive and control loads than for resistive loads:
- Output ripple. The switching ripple on the module output adds to the gate-drive rail noise; compare the ripple specification at the operating load and input voltage, not the best-case number.
- Transient response. A gate-drive pulse draws a current burst at each switching edge; the module’s recovery time and output capacitance decide how far the rail dips. If the dip approaches the driver’s UVLO threshold, the module is undersized even when the average power looks fine.
- Cross-regulation. Multi-output modules trade regulation between channels; a logic rail and a gate-drive rail on the same module can disturb each other under asymmetric loads. Check the cross-regulation specification against the actual load profile.
These three specifications are where the module’s data sheet meets the driver’s requirements; the gate-drive guide’s sizing and UVLO logic define the acceptable rail, and the module datasheet defines what it delivers.
The input side matters too: the module’s input range must tolerate the system rail’s transients, and its input ripple and EMI behavior contribute to the board’s emissions. Check the input filter requirement and the module’s conducted-emission behavior against the system’s compliance target rather than assuming the module is automatically clean.
Industrial Control and Sensor Power
Beyond gate drive, isolated modules power field-bus transceivers, sensor interfaces, and control boards where galvanic isolation protects the logic from ground loops and transients. The same selection rules apply, with the isolation rating and the creepage/clearance of the module’s package matching the system’s working voltage and pollution degree. The module’s certification—against standards such as IEC/UL 62368-1 or the applicable industrial safety framework—is part of the selection, not an afterthought.
A Selection Path for Isolated DC-DC Modules
- Define the load: voltage, average and peak power, ripple tolerance, and the transient profile.
- Choose the isolation class from the end-equipment standard and the working voltage.
- Check the module’s derating at the operating temperature and input range.
- Verify the transient response against the load’s peak (especially gate-drive pulses).
- Confirm the certification and the isolation rating table in the module datasheet.
- Check the package and footprint against the board, including creepage and clearance.
For the power module families available, the product catalog on the Good-Ark site is the entry point; to request the module family table, derating curves, and the isolation certificates, contact Good-Ark with your load and isolation requirements.
Frequently Asked Questions
How much power does a gate-driver supply need? Estimate Qg × VGS × fsw per channel plus the driver quiescent power, then add margin. A typical multi-channel SiC or IGBT drive needs a few watts; size the module for the peak, not just the average.
What isolation rating do I need? It comes from the end-equipment safety standard and the working voltage—functional isolation for basic separation, reinforced for user-accessible or mains-connected contexts. The module’s certificate and rating table are the evidence.
Can a module power both logic and gate drive? Often yes, through multiple output channels or a single rail with separate regulation—but the noise from the switching side must not corrupt the logic rail. Check the module’s cross-regulation and ripple specifications.
Where can I check the module families and ratings? The product catalog covers the power module families, and the contact page connects you to the team with your input, output, and isolation requirements.
The Module Moves the Risk
An isolated DC-DC module moves the transformer, the control loop, and the isolation certification from the system designer to a qualified component. Size it from the load’s peak, match the isolation class to the standard, verify the derating at temperature, and confirm the transient response against the real load. When the module’s ratings and the application agree, the isolated rail becomes a bought-and-tested asset instead of a design risk.